Ideally, nitrous (and fuel) are injected after the carb (or EFI), as close to the engine as possible. In this type of engine, that place ends up being the small adapter/manifold between the carb and the reed block. There wasn't a whole lot of room here, but I was convinced it was possible without the machining of a new, larger spacer. Also, the carb intake faces the rear tire and there wasn't a whole lot of clearance to add a larger intake manifold spacer. In the middle picture you can see a nice shot of how thick the manifold is and where the nitrous injection has to go. Ideally I would have had a new manifold machined, but I don't know any CNC machinists.

By drilling a couple holes, and inserting some custom made tubing/fogger nozzles I was able to create my own home-grown direct-port nitrous injector manifold without affecting the intake bore at all. There may be a tiny bit of turbulence around the holes but, shit, its a pocket bike. The socket fit in there perfectly to keep the tubing perfectly flush with the bore. A little JB weld is keeping the nylon tubing connected to the fogger tubing connected to the manifold. I'm curious to see if the JB will actually hold up.

Well, the first manifold didn't hold up for 5 minutes. The macroline was too hard to bend (even heated) and the brass ended up coming loose and bending. Here is the second version, which I like much, much better. Hopefully it won't put too much heat into the nitrous. Actually, I know it will in this configuration, but I don't care. You can see the solenoids mounted to a bracket I fabricated.

Jetting was accomplished with a #80 drill bit. Not much thicker than a hair, its about .38mm in diameter. A hole that small tames the 900psi of nitrous down to a nice whisper for the small engine. I think the bottle mounting location looks cool, but needs to be made more permanent. At this point the wiring is complete, but not all tidy until it works. I'm leaking a lot of fuel too. Nitrous activation is fully electronic.

I have to say the nitrous system is a success. At this point, I think the nitrous is actually hindering the top speed of the bike. At the top end I believe the bike is running into a lean condition and simply running out of fuel. That said, the kick from the nitrous is great. I'd say it accelerates at least 100% faster when the nitrous is on. I'd really like to get a Walbro WT-603 carb which would give a far greater range of adjustability. I've already spent too much money on this project, no more.